Electric induction apparatus



y 1 c. w. KRONMILLER 2,553,591

ELECTRIC INDUCTION APPARATUS Filed Aug. 16, 1946 pi .5.. 1 1g? 2/ g 25 1/26 0 t1: 3; it 0 III) 9 1/" Inventor:

His Attorney.

Patented May 22, 1951 UNITED 2,553,591 ELECTRIC INDUCTIQN APPARATUS Charles W. K'ronmiller, Fort Wayne, Ind., assignor to General Electric "company, a corporation of New York Application August 16, 1946, Serial No. 690,855 3 Claims. (01. 1 71 777) This invention relates to electric induction apparatus and more particularly to improvements in high reactance transformers which are used as ballasts for electric discharge devices.

By high reactance transformer is meant a transformer having an abnormally high leakage (or efiective series) reactance so that the device .has an abnormal amount of regulation. Transformers of this type have been used for ballasting electric discharge devices with a capacitor connected in seriesin the circuit so that the current is leading. It has been found that when the reluctance of the portion of the transformer core which is most intimately associated with the secondary winding has a high reluctance section the operation of such leading current circuits is improved, both as to currentand voltage wave form and also the amount of material, both copper and iron, which is necessary in order to obtain the proper degreeof regulation, that is 'to say, the proper drop between a relatively high open circuit or no-load voltage and a relatively low closed circuit or full-load voltage, is 'reduced. That invention is disclosed and claimed in application Serial Number 731,559 filed February 28, 1947 in the name of Harold W. Lordand assigned to the same assignee.

.In accordance with this invention there i'sprovided an improved electric induction apparatus embodying certain novel structural features for carrying the Lord invention into effect.

An object of the invention is to provide a new and improved electric induction apparatus.

Another object of the invention is to provide a new and improved magnetic core for electric induction apparatus. I i

A further object of the invention is to provide an efiicient andinexpensiye'two-lamp ballast.

The invention will be better understood,;from the" following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

In the drawing Fig. 1 is a side view of an apparatus embodying my invention with the winding shown in cross section, Fig. 2 is a sectional view taken on line 22 of Fig. 1, Fig. 3 is a circuit diagram of the electrical connections of the device shown in Figs. 1 and 2, Fig. 4 and Fig. 5 illustrate modifications.

Referring to the drawing and more particularly to Fig. 1, there is shown therein a shelltype core I consistin of E-shaped packets 2 and 3 of E-shaped core laminations. The legs of the laminations of the packet 2 are relatively long and the legs of the laminations of the packet 3 the primary winding 9.

2 are relatively short. The packets have the ends of their legs butted against each other at 4. As shown most clearly in Fig. 2, a predetermined number of the intermediate laminations in the core packet 3 have shorter legs than the laminations in the same packet which are on opposite sides of the central portion, thereby to form a central gap 5 which is bridged by the longer portions 8 of the outer laminations of the packet 3. This bridged gap may exist in the center leg of the core only or it may exist inaddition in the yokes, as shown by the dashed lines I in Fig. 1 which indicate the ends of the legs of the shorter central laminations in the core packet 3.

It will be obvious also that it is not essential that the gap 5 be in the packet 3 and it may also be in the packet 2 by making the legs of a certain number of intermediate laminations in the core packet 2 shorter than the other legs on both sides of the central portion.

Magnetic shunts or inserts 8 are inserted between the center leg of the packet 2 and the outer yoke portions. Mounted on the center leg between the magnetic shunts is a winding 9 and mounted on the center leg between the magnetic shunts and opposite ends of the core are coils Ill and I I. As shown in Fig. 3, coil 9 ma be a cornmon primary winding for a two-circuit reactance type autotransformer in which coil It) is connected in series with coil 9 to form therewith a secondary Winding between a pair of terminals i2 and I3 for a lag lamp circuit and coil II is connected in series with coil 9 so as to constitute a secondary winding of a reactance transformer for supplying current between common terminal I2 and a terminal M for a lead lamp circuit. Connected. in this circuit is a capacitor I5 and ordinarily this capacitor is connected betwee' the terminal l4 and the winding II and is mounted in the same container or housing with the transformer structure shown in Figs. 1 and 2.

A supply circuit I6 is shown connected across A suitable lamp I1 is connected between terminals I2 and I3 and another lamp I8 is connected between terminals l2 and Id. These lamps are provided with starters IQ of any suitable type.

It will be observed from the drawing that the bridged air gap 5 and the restricted sections 6 of the core are in the portion thereof which is most intimately associated with the secondary coil I I for the lead circuit and that therefore the magnetic reluctance of this portion of the core is higher than the portion of the core which is most intimately associated with the secondary winding Hi for the lag circuit.

In the modification shown in Fig. 4, the primary winding 9, the extended secondary winding ID for the lagging current circuit and the extended winding H for the leading current circuit are mounted on a straight core winding leg '20. The core is completed by means of two oppositely disposed 4-legged yoke members 2|. One end leg 22 of each of these yoke members is longer than its other three legs, and as shown, legs 22 are in contact with opposite sides of one end of the center winding leg 29. The intermediate legs are located between the windings so as to provide leakage flux paths and the other end legs which are indicated at 23, provide gaps 24 in the portion of the core which is most intimately associated with the secondary winding II for the leading current circuit.

In Fig. 5, there is shown a core type core comprising a long-legged U-shaped core member 25 and a short-legged U-shaped core portion 26. The primary winding is shown as comprising two coils 9 and 9. The secondary winding for the lagging current circuit is shown as comprising two coils I and I9, and similarly, the secondary winding for the leading current circuit is shown as comprising coils l l and H. The required reactance or leakage flux is obtained by a relative ly wide, axial or longitudinal displacement between the three different windings. The increase in reluctance in the portion of the core which is most intimately associated with the leading current secondary winding is obtained by gaps 21 between the adjacent ends of the legs of the U- shaped core portions 25 and 26. It is not essential that the gaps 2'! be inside the coils H and II, but it is essential that they be to the right of the space between the primary winding and the leading current secondary winding because 1 it is within this space that the leakage flux leaves the core.

While there have been shown and described particular embodiments of this invention, it will be obvious to those skilled in the art that various changes and modifications can be made therein without departing from the invention and, therefore, it is aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, an E-shaped packet of stacked long-legged E-shaped core punchings, a similar packet of stacked short-legged E-shaped core punchings, the ends of the legs of said packets being butted together toform a shell-type core, a predetermined number of intermediate punchings of at least one of said packets having shorter legs than the outer punchings of said packet whereby a bridged gap is formed between said packets and spaced magnetic shunts between the center and outer legs of the longlegged packet.

2. In combination, an E-shaped packet of stacked long-legged E-shaped core punchings, a similar packet of stacked short-legged E-shaped core punchings, the ends of the legs of said packets being butted together to form a shell-type core, a predetermined number of intermediate punchings of at least one of said packets having shorter legs than the outer punchings of said packet whereby a bridged gap is formed between said packets, spaced magnetic shunts between the center and outer legs of the long-legged packet, a common autotransformer winding on the center leg of said core between said magnetic shunts, separate extended secondary windings on the center leg of said core between said magnetic shunts and the ends of said center leg, a pair of lead circuit terminals, said common primary winding and the secondary winding which is on the portion of the core which is most intimately associated with said bridged gap being serially autotransformer connected between said lead terminals, a pair of lag circuit terminals, said common primary winding and the other secondary winding being serially autotransformer connected between said lag circuit terminals.

3. In combination, an E-shaped packet of stacked long-legged E-shaped core punchings, a similar packet of stacked short-legged E-shaped core punchings, the ends of the legs of said packets being butted together to form a shelltype transformer core, a predetermined number of intermediate punchings of at least one of said packets having shorter legs than the outer punchings of said packet whereby a bridged gap is formed between said packets, spaced magnetic shunts between the center and outer legs of the long-legged packet, a common autotransformer winding on the center leg of said core between said magnetic shunts, separate extending secondary windings on the center leg of said core between said magnetic shunts and the ends of said center leg, a pair of lead circuit terminals, a capacitor, said common primary winding, said capacitor and the secondary winding which is on the portion of the core which is most intimately associated with said bridged gap being serially autotransformer connected between said lead terminals, a pair of lag circuit terminals, said common primary winding and the other secondary winding being serially autotransformer connected between said lag circuit terminals.

CHARLES W. KRONMILLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,752,109 Prince Mar. 25, 1930 1,942,535 Cairns Jan. 9, 1934 2,312,768 Mitchell Mar. 2, 1943 2,382,638 Keiser Aug. 14, 1945 2,404,254 Short July 16, 1946 2,436,925 Haug et al. Mar. 2, 1948 2,461,947 Berger Feb. 15, 1949 

